FFmpeg sws_scale幀伸縮和像素轉換

/*
將保存有YUV420像素格式的幀，轉換成BGR24像素格式，並且按照幀指定的尺寸進行縮放
*/
void VideoDecodec::ConvertYUVFrameToBGRFrame(AVFrame* pYUVFrame, AVFrame* pBGRFrame)
{
 int nBGRFrameSize = av_image_get_buffer_size(AV_PIX_FMT_BGR24, pBGRFrame->width, pBGRFrame->height, 1);
 uint8_t* pszBGRBuffer = (uint8_t*)av_malloc(nBGRFrameSize);

 //將pszBGRBuffer掛載在pBGRFrame幀的圖片緩存指針，需要手動刪除
 av_image_fill_arrays(pBGRFrame->data, pBGRFrame->linesize, pszBGRBuffer, AV_PIX_FMT_BGR24, pBGRFrame->width, pBGRFrame->height, 1);

 struct SwsContext *pSwsCtx = sws_getContext(pYUVFrame->width, pYUVFrame->height, AV_PIX_FMT_YUVJ420P,
  pBGRFrame->width, pBGRFrame->height, AV_PIX_FMT_BGR24,
  SWS_POINT, NULL, NULL, NULL);

 //注意需要將0填充srcSliceY,否則調用失敗
 sws_scale(pSwsCtx, pYUVFrame->data,
  pYUVFrame->linesize, 0, pYUVFrame->height,
  pBGRFrame->data, pBGRFrame->linesize);

 //釋放環境

 sws_freeContext(pSwsCtx);
}

進階

sws_scale提供如下的算法對圖像進行伸縮變換

/* values for the flags, the stuff on the command line is different */
#define SWS_FAST_BILINEAR     1
#define SWS_BILINEAR          2
#define SWS_BICUBIC           4
#define SWS_X                 8
#define SWS_POINT          0x10
#define SWS_AREA           0x20
#define SWS_BICUBLIN       0x40
#define SWS_GAUSS          0x80
#define SWS_SINC          0x100
#define SWS_LANCZOS       0x200
#define SWS_SPLINE        0x400

目前需要對圖像像素進行壓縮，方便算法加快識別，每種算法生成的像素圖片尺寸差不多